In a memory cell of a non-volatile semiconductor storage device, for example, during a data write period, electric charges are written from a semiconductor substrate through a tunnel insulating film to a charge storage region; and for example, during a data erase period, electric charges are extracted from the charge storage region through the tunnel insulating film to the semiconductor substrate. Since stress may be exerted to the tunnel insulating film every time when the electric charges pass through the tunnel insulating film, the tunnel insulating film may be deteriorated. Therefore, it is preferable to improve reliability of the non-volatile semiconductor storage device.